I've been facing this problem for a while. Each time I press ctrl + space to open a suggestion, Intellij tries to index something and close a suggestion window. Has anyone had a problem like this?

https://kotlinlang.org/docs/reference/ Kotlin lastest version is 1.4.10. But I want refer to v1.3.72 docs, how do that? Help me. What link is kotlin old version docs?

hello there, i may have this kind of code

fun main(){
  val list =  listOf(1, 10,-1, -2, 3,12)
  val joined = list.joinToString(" + ")
  println("${joined} = 10")
}

which prints the list as string with + sine added(

"1 + 10 + -1 + -2 + 3 + 12 = 10"

). but i wan't it to really add and return either true or false. how can i do that

fun foo() = println("No receiver")
fun Int.foo() = println("My receiver is $this")

with(42) { foo() } // will print 'My receiver is 42' but I want 'No receiver'

Is it somehow possible to call the function without receiver, although one is given by the current scope?

hi, is there a compiler setting to mark all objects returned by java methods nullable? e.g. we are using jooq, a library to write type safe sql queries. it has several

fetch

methods, all of which might or might not return a value, depending on what the sql returns. The compiler doesn;t recognize it's nullable and so we are always in danger to produce NPEs...

view.findViewById<AppCompatTextView>(
    R.id.strike_price
)?.let {
    it.text = price.toString()
}

Would you

nit

this, or request changes? 1️⃣ nit 2️⃣ request changes, unnecessary use of

let

What's your opinion on using top level functions with capital letter as factory functions? I notice people doing this more and more

fun User(...) : User? {
   // if invalid input return null
   return User(..)
}

data class User(...)

According to the official documentation, "SAM conversions only work for interfaces, not for abstract classes, even if those also have just a single abstract method." But I just tried it with an Abstract Class and it seems to work. Did I not understand the documentation properly or this is now possible in New Kotlin version? 🤔 https://kotlinlang.org/docs/reference/java-interop.html#sam-conversions

Is

foo

being

null

inside the init block expected behavior? Doesn't seem right for a property that's declared not null. Printing

foo

directly results in an error. Run code in kotlin playground

sometimes I find my self misusing the

@Deprecated

annotation just to remind me some critical logic when using a specific variable (in the context of some native code port).. has anyone a better idea?

Any better workaround for nullable destructuring?

val (p1,p2) = pair ?: null to null

is there a way to sort only a ArrayList subrange?

while (value.links.next != null) {

any chance to smartcast value.links.next to non-null inside the loop? Basically looking for a counterpart to

nullable?.let { it is not null }

Any jetbrains people around that can answer some questions about

code with me

?

I’m trying to add a property to an interface with a default value, that is no problem. But thats a function,  and I need a property that can change Why isn’t contracts supported for properties? This is my code:

interface PrimitiveType<T> {
    var value: T?
}

interface Defaultable<T> {
    var defaultValue: T
}

@ExperimentalContracts
fun <T> PrimitiveType<T>.defaultValue() : T {
    contract {
        returns() implies ( this@defaultValue is Defaultable<*>)
    }

    return this.value!!
}


@ExperimentalContracts
fun <T> PrimitiveType<T>.editValue() : T {
    contract {
        returns() implies ( this@editValue is Defaultable<*>)
    }

    return this.value!!
}

@ExperimentalContracts
fun <T> PrimitiveType<T>.setEditValue(value: T) {
    contract {
        returns() implies ( this@setEditValue is Defaultable<*>)
    }

    this.value = value
}

Does this create one million lists of the 2 same strings or is this optimized somehow? I’m used to declaring such list of accepted values as a

val

before but I’m not sure if it’s needed

myListWithOneMillionElements.filter { it.a in listOf("a", "b") }

This is a bit of a n00bish question… but if I’m trying to match an email pattern with a regex… and I have some pattern “patern”.toRegex()… what is the proper way to find out if a string matches that regex? in my case I’m using the RFC email address regex to validate, but I’m getting false results when I do. Here’s the link to the regex

val regex = "Regex here".toRegex()
regex.matches("<mailto:first.last@test.com|first.last@test.com>")

what am I missing?

I have an Android project in AndroidStudio 4.2 Canary 16 which has a dependency on an external Kotlin library locally published to maven (written in Idea 2020.2). Both project and library use Kotlin 1.4.10 and the new backend compiler. The problem I have is that I'm able to execute Android code which refers to objects from the Kotlin library but cannot access the objects directly during debugging via breakpoints or using Evaluate Expression. For example given library class

class Person(val name: String) {

fun greeting() = "Hello, I'm $name"

}

I can run this test in Android Studio:

class ExampleUnitTest {

@Test

fun name() {

val person = Person("Jane")

assert(person.name == "Jane")

}

}

but... If I set a non-suspending breakpoint to print out the value of person.name or a set a suspending breakpoint and use Evaluate Expression to evaluate person.name I get the error: Class 'uk.co.telesense.controller.Person' is compiled by a new Kotlin compiler backend and cannot be loaded by the old compiler If I debug the test with no breakpoints it runs green. Any idea what's going on here? In the kotlin library I have:

compileKotlin {

kotlinOptions.useIR = true

}

compileTestKotlin {

kotlinOptions.useIR = true

}

in the Android Studio project I have

buildscript {

ext.kotlin_version = '1.4.10'

...

dependencies {

classpath 'com.android.tools.build:gradle:4.2.0-alpha15'

classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

}

...

}

I hope that makes sense! Any ideas?

I've got a class that has a constructor with a single parameter and I want to add a couple of different "public" read only members to the class as well. there is a expensive algorithm to calculate the values of each of the members based on the constuctur parameters. How can I run the algorithm only once and populate vals?

Hi everyone, i'm new to kotlin and i need help in regarding parsing json to sealed class using kotlin.serialization library, whats the difference between serializer and serialName

Is there any HTTP request kotlin standard library which is wrapped with kotlin.jvm why I am asking this is most of online compilers like repl, sololearn, play kotlin have no gradle support which wont let me use libs like okhtpp..

In kotlin-multiplatform targeting js, Long values are represented as an object containing the top and bottom 32 bits of the value as separate fields ({low: lowbits, high: highbits, value: zzzzzzzzzz}) . Is there any way to hint to the compiler that the values are less than Number.MAX_SAFE_INTEGER, and that they should be represented in javascript as a bare Number, or to otherwise pass a number greater than 1<<31 back into native javascript code?

https://codingcompetitions.withgoogle.com/kickstart/round/000000000019ffc7/00000000001d3f56 i was trying to solve this using kotlin my code passes the test cases but after submission it doesn't get accepted (same algo is accepted for c++ code ) please help

What would the best place be to post suggestions for the Kotlin language on the whole? I'm digging into Jetpack Compose and it seems like they ran into the same issue I keep struggling with. The simple lack of "multi extension" functions. IDK if there is a good reason they don't already exist, or if someone has already proposed they just be added to the language, but I think they would be hugely useful. eg.

data class First(
    val partOfFirst: String
)
data class Second(
    val partOfSecond: String
)
fun First.Second.multiExtension() {
    println(partOfFirst + partOfSecond)
}
fun main() {
    First("hello ").apply {
        Second("world").apply {
            //possible because First and Second are both in this scope.
            multiExtension()
        }
    }
}

class C
object O {
    operator fun C.plus(other: C): C = this
    operator fun C.inc(): C = this
}

Could anyone please explain to me why the second function (inc) is illegal/doesn't compile, but the first is okay (plus)? Fails with

'operator' modifier is inapplicable on this function: receiver must be a supertype of the return type.

Isn't the receiver (

C.

) a supertype of the return type (

: C

) in both cases? This compiles and runs if I move the fun declaration of inc outside the object to root level BTW.

Is there a generally accepted pattern to deal with variables that never change after being set, but they arn't known at object construction time? lateinit helps w/ the late-part, but not the val part. It'd be nice if the compiler could help if anyone is trying to change it.

is there any benefit in declaring the types of the lambda parameters?

Ran into another issue in my codebase. It took me a little while to track it down, but I suspect it might be a compiler error? Seems data classes don't play well with overriding interface properties with

@JvmField

annotations:

interface Interface {
    val value: Int
}

data class Implementation(@JvmField override val value: Int) : Interface

class Test {
    @Test
    fun test() {
        assertEquals(Implementation(123), Implementation(123))
    }
}

It works if I do one of three things: • don't override the interface variable • remove the

@JvmField

annotation • make it a normal (non-data class) Dunno if this is intended to not be permitted, or a bug in the generated

equals

code. Either way if I leave it as is it compiles, but then throws an exception at runtime: